This project focuses on the molecular mechanism of specific interactions between proteins and transfer RNAs and related areas. Particular emphasis is placed on aminoacyl tRNA synthetases. In addition, new proteins, with unknown biological functions, which bind to specific transfer RNAs are sought and studied; the biological role of these proteins and their means of recognizing specific transfer RNAs is of interest. Sequencing of peptides involved in photo-crosslinked synthetase-ATP and synthetase-tRNA complexes is explored with an eye toward elucidating structural features of these complexes. Other studies aim at eludicating the mechanism of specific protein-transfer RNA interactions by utilizing special procedures such as tritium labeling of transfer RNA. BIBLIOGRAPHIC REFERENCES: P. R. Schimmel, The Interaction of Transfer RNAs with Aminoacyl Transfer RNA Synthetases, Proceedings of the Tenth FEBS Meeting, 219 (1975). P. R. Schimmel, G. P. Budzik, S. S. M. Lam, and H. J. P. Schoemaker, In Vitro Studies of Photochemically Crosslinked Protein-Nucleic Acid Complexes. Determination of Crosslinked Regions and Structural Relationships in Specific Complexes, in Aging, Carcinogenesis and Radiation Biology: The Role of Nucleic Acid Addition Reactions, K. C. Smith, Ed., Plenum Press, New York, p. 123 (1976).